In recent years, laser scanning systems have been proposed which are capable of scanning a record medium such as a document in a read mode of operation or to record information on a laser sensitive medium in a write mode of operation. The prior art systems have generally utilized a multifaceted rotating polygon which is driven at a constant speed. However, the large degree of accuracy necessitated and machine tolerance required in grinding and polishing each of the facets to avoid errors which can be caused by misaligned facets have made the cost of such multifaceted polygons relatively expensive. Manufacturers of such scanning systems have sought, usually unsuccessfully, alternate ways of manufacturing the multifaceted polygons at reduced cost. In order to minimize facet induced system erors, additional optics associated with the rotating polygon has been provided. However, this also adds to the cost and complexity of the system.
An alternative type of scanning device which can be utilized is a galvanometer or other type of mechanical oscillating mirror devices. If the galvanometer is utilized in its linear mode of operation, i.e. it is driven by a ramp current pulse, its low scanning speed and the increased cost due to the requirement of providing the ramp current pulse makes its use relatively inefficient. Much higher speeds can be achieved with galvanometers if they operate in a resonating mode. However, the sinusoidal variations in the scanning velocity, unless compensated, will result in nonuniformity in the data flow, or bit density, (resolution) of the data in the read and write modes of operation. The galvanometer mirror generally would have a slow angular velocity towards the end portion of its displacement and a faster angular velocity during the middle portion. Obviously, these nonlinearities produce corresponding nonlinearities in the scanning velocity of the beam.